In general, silver halide color photographic materials contain silver halide emulsion layers sensitive to light beams having three primary colors, red, green and blue, respectively, and reproduce color images using a so-called subtractive color process, or a process in which three kinds of couplers incorporated in separate emulsion layers are made to form their colors bearing a complementary relationship to the colors of light beams to which the corresponding layers are sensitive respectively. Color images obtained by subjecting such silver halide color photographic materials as described above to photographic processing are generally constituted of azomethine or indoaniline dyes formed by the reaction of couplers with the oxidation product of an aromatic primary amine color developing agent.
However, even the color photographic materials which form color images on such an excellent system as described above have being come to cause dissatisfaction among users who continue to request a higher level of image quality. In particular, developed color images obtained from yellow dye forming couplers still have some disadvantages to be surmounted. Firstly, absorption coefficients of yellow dyes formed from conventional couplers were lower than those of dyes obtained from cyan dye- and magenta dye-forming couplers, so that it was necessary to use a yellow dye-forming coupler in a larger amount in order to ensure the same density to the yellow image as those of cyan and magenta images. Secondly, yellow dyes formed from conventional couplers did not always have a hue satisfactory for faithful reproduction of the color of a subject. Thirdly, yellow dyes formed and yellow dye-forming couplers remaining undeveloped were unstable to light, moisture and heat, so that the dye images suffered from discoloration or color change, and the white background stained when exposed to sunlight for a long time or when stored under high temperature and high humidity conditions, resulting in the deterioration of image quality.
With the intention of solving these problems, attempts have been made to promote color development by improving upon couplers themselves or by allowing particular compounds, e.g., specific phenol or sulfonamido compounds, to be present together with couplers. However, such attempts produced unsatisfactory results.
On the other hand, it is known to use a discoloration inhibitor and an ultraviolet absorbent to make improvements in image fastness. Examples of compounds known as discoloration inhibitors include hydroquinones, hindered phenols, catechols, gallic acid esters, aminophenols, hindered amines, chromanols, indanes, ethers or esters obtained by silylating, acylating or alkylating the phenolic hydroxyl groups of those compounds, metal complex salts of those compounds, and so on.
However, such compounds produced very little effect in increasing the absorption coefficients of the yellow dyes obtained. Moreover, their effects on yellow dyes were insufficient, even though they had considerable effects on magenta dyes. What was worse, they caused a change in hue, the generation of fog, a poorly dispersed condition, or the deposition of crystallites after coating emulsions.
More specifically, the application of amine or hydrazine derivatives with the intention of ensuring fastness for dye images obtained from yellow dye-forming couplers are described in JP-A-02-262654 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-02-181145, Japanese Patent Application No. 02-35681, JP-A-02-150841, JP-A-02-181753, JP-A-02-148034, and so on.
In addition, the combined use of amine derivatives with a specific structure and other compounds with a special structure is proposed in JP-A-02-239149.
Moreover, pentavalent phosphorus compounds with a specific structure are proposed in JP-A-63-113536, JP-A-01-289952, JP-A-01-284853 and JP-A-63-256952 for affording fastness to the dye images obtained from yellow dye-forming couplers and for improving upon spectral absorption characteristics of said dye images.
Also, trivalent phosphorus compounds with a specific structure are proposed in JP-B-48-32728 (The term "JP-B" as used herein means an "examined Japanese patent publication"), JP-B-63-19518, JP-A-55-67741, JP-A-61-137150, JP-A-63-301941, JP-A-02-12146 and JP-A-03-25437.
The effects accomplished by the combination of those compounds and hitherto known yellow dye-forming couplers are insufficient with regard to the photographic characteristics as described above, image fastness and so on.
In this sense, it has been desired to not only make improvements in color formation characteristics of couplers and photographic characteristics of the dye images formed therefrom, but also to inhibit the dye images from discoloring or changing their colors, without affecting adversely the aforementioned characteristics.